1. Make sure that density of the material, the target hollow cylinder to be build with, is available. Note: Check Aqua-Calc density table for this material. If your material is not present in the density table, let us know of your particular substance, so we can add the material to the database.
2. You need radius/diameter of both, the inside (inner) and outside (outer) cylinder surfaces.
3. Calculate volume of the outer cylinder. See http://www.aqua-calc.com/calculate/volume-cylinder.
4. Calculate volume of the inner cylinder. See http://www.aqua-calc.com/calculate/volume-cylinder.
5. Subtract volume of the inner cylinder from the outer one. This is the actual volume of the material of your hollow cylinder.
6. Use Aqua-Calc volume to weight calculator to calculate weight of the material based on the material density, and the volume calculated in the previous step.